The present invention concerns a procedure for producing a poly-alpha-olefine-type lubricant by oligomerizing olefines with the aid of a BF.sub.3 cocatalyst complex.
The production methods of a poly-alpha-olefine lubricants known in the art generally consist of the following phases: oligomerizing the starting olefine material; removal of catalyst residues; fractional distillation of the product; and hydration. The most commonly used oligomerization catalysts are of the so-called Friedel-Crafts type, primarily boron trifluoride, in addition to which various alcohols are used as so-called cocatalysts or promotors (please see, e.g., U.S. Pat. Nos. 3,780,128; 4,032,591; 4,376,222; 4,409,415; and 4,587,368), or aluminum halogenides are used (please see, e.g., U.S. Pat. Nos. 2,559,984; 3,637,503; and 3,652,706).
Among these catalysts, boron trifluoride, due to high-level toxicity of fluorine compounds, specifically involves considerable removal and waste handling problems related to catalyst residues, thus resulting in extremely high or remarkable economic expenses.
Known procedures used for removing catalyst residues are primarily washing of an oligomerizing mixture with a concentrated NaOH water solution, and precipitation of the fluorine compounds in the form of solid inorganic salts.
Additionally, procedures for circulating the BF.sub.3 catalyst have been developed, such as by binding it to a solid cocatalyst (silicon dioxide) whereby only the part of the BF.sub.3 soluble in the oligomerization product is left therein, the separation of which from the product is accomplished with filler piece columns operating at reduced pressure (U.S. Pat. No. 4,263,467). Also, liquid phase separation between the BF.sub.3 alcohol catalyst complex and the oligomer product can be performed. Utilization of both these technologies leads, however, to the use of only a BF.sub.3 cocatalyst system (BF.sub.3 *SiO.sub.2 or a BF.sub.3 *alcohol) which does not allow for an optimum oligomerization result and which causes problems in the production of a high-quality product.